Human thermal comfort is the function of both the air conditions (that is, temperature and air velocity) as well as the radiant environment of the occupants. Alternative types of heating systems, known as radiant heating systems, that use fluid circulated in the floors and/or walls of a building instead of forced hot air are common. Higher floor and/or wall temperatures provide a warm, radiant environment for the occupants which allows the same degree of comfort with a lowered air temperature. Each degree of setpoint temperature reduction can save 2 to 5% of the heat required for a building. In addition, the power required to circulate fluid through tubes in the floor is less than the power required to circulate warm air to deliver the same amount of heat. Further, the circulating air makes the occupant feel colder, negating some of the warming effect.
The most common method of radiant heating, via hydronic fluid circulation, has drawbacks. First, the necessary fluid lines must be embedded in the floor of the space, at significant expense. Retrofit applications of radiant heating are much more expensive, because retrofitting the tubes requires either replacement of the floor, or the addition of a new layer of concrete in which to embed the tubes, which adds further costs and construction complexities. Second, the thermal energy is delivered by conduction through the floor structure, and so the entire mass of the floor must be heated, leading to a large time lag between the initiation of heating from the system and the temperature rise of the floor—typically 30 minutes to one hour. This makes it impossible for the thermal control system to respond to many normal changes in the heating load or changes in the desired temperature of the room. Finally, common floor coverings and furnishings such as rugs, carpets, furniture and cabinets act as insulators to conduction of heat from the floor, which reduces the effectiveness of the heating and further increases the time lag in responding to changes in load and set point. Thus, there remains a need in the art for applications of radiant heating that avoid such disadvantages of previously known systems.
Further, skylight systems have been provided for illuminating a space below a skylight unit. However, there are a number of practical problems regarding the control of illumination levels with current skylight practices. For instance, most existing skylights have no active control elements at all. The control of illumination levels in the space is completely dependent on adjusting the levels of artificial illumination. Further, current skylight systems that use other modulation techniques such as shades or dampers also suffer drawbacks. For instance, modulation consists of reflecting or blocking the undesired levels of light. The excess light is either reflected back to the sky, which causes it to be wasted, or is absorbed by the modulating surface, which can overheat the skylight. Further, modulation by shades or dampers requires either movement of the shade surface by a significant fraction of the cross-section of the skylight area, or a large angle deflection of the dampers. Consequently, for practically sized motors and drive mechanisms, it is impossible to effect changes in the illumination levels in the time scale of less than one second. Still further, none of the existing systems that are known to the inventor herein are self-contained such that the skylight measures its own delivered illumination levels and adjusts its own dampers accordingly. Modulation of the lighting levels is performed by external systems tied into building system controls which increases system cost and complexity. Thus, there remains a need in the art for controlling the amount of illumination provided by skylight systems that may be more easily implemented than previously known systems.